Pop his name into the Insolvency Register search page ( https://www.insolvencydirect.bis.gov.uk/eiir/ ) and this will give you details of the IVA. Click on the name and it will give you details of his IP. Lodge a claim with the IP. You will probably need some sort of proof of the debt.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014 http://foggy.blogs.iva.co.uk